| Bio asphalt as derived from biomass renewable energy,is the ideal alternative of petroleum asphalt,became the various countries' road materials research hotspot in recent years.But there are some defects such as high temperature aging,easy to brittle fracture at low temperature,water stability,need to be modified by physical and chemical means.The purpose of paper is to study how poly phosphoric acid(PPA)modified bio asphalt preparation and modification technology,and the more PPA modified bio asphalt road use performance of asphalt and it's mixture were studied.In this paper,we use straw pyrolysis bio-oil to prepare bio asphalt by cold water extraction method,and consider the preparation of bio asphalt normal performance.Study found that cold water extraction method can get rid of light component in bio-oil soluble in water,heavy components is the bio asphalt,this method is high efficiency and energy saving,easy operation and quick.Bio asphalt has bigger consistency,better high temperature performance than petroleum asphalt.However the hard brittle at low temperature and high temperature aging defects should be improved.In addition,the adhesiveness of bio asphalt and aggregate should be paid attention to.In this paper,the bio modified binder(BMB)was prepared by mixing with Esso 70# asphalt,and the performance differences between the BMB and Esso 70# asphalt were compared and analyzed.The results showed that the penetration degree and ductility of BMB were better than bio asphalt,but the softening point were lower than that,meanwhile,the degree of adhesion was also significantly improved.Through the comparison the viscosity curve of various BMB with different component bio asphalt,combined with performance test results of BMB,the conditions of preparation BMB were determined as follows: the mass ratio of bio asphalt to petroleum asphalt is 2:8;the stirring temperature is 120?;the mixing time is 30 minutes.In this paper,with PPA modified BMB,optimization of preparation process was determined as follows: material addition sequence should be used first preparation of PPA modified asphalt,and then its way of mixing with pure bio asphalt;mixing temperature should be controlled at about 120?;stirring time should be controlled at about 30 minutes better.Penetration of BMB after PPA modified reduced and ductility decreased,softening point increased,while the anti rutting performance?anti fatigue performance and crack resistance at low temperature has risen,mixing and compaction temperature dropped to a certain extent.The performance grade of the BMB without PPA is PG58-22,and the performance grade is PG64-28.It showed that PPA has function of widening the temperature range.At the same time,the aging resistance of PPA modified bio asphalt has some limitations compared with that before modification.Finally,this paper analyzes the PPA modified bio asphalt mixture,and compares it with Esso 70# asphalt mixture and BMB mixture.Marshall test results show that PPA modified bio asphalt has higher Marshall stability and dynamic stability,flow approximation is same as that of other two kinds of asphalt mixture,the results show that PPA can effectively improve the anti rutting performance of asphalt pavement.Bending failure test results show that PPA can improve the low temperature crack resistance of BMB mixture.However,the water stability of PPA modified bio asphalt is poor.In the end of this study,the anti stripping agent is added to make the mixture meet the specification requirements. |
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